The neglected history of Oceanic Anoxic Event 1b: insights and new data from the Poggio le Guaine section (Umbria-Marche Basin)

At Poggio le Guaine (central Italy), a continuous and undisturbed section of central western Tethyan pelagic sediments deposited during the latest Aptian and earliest Albian, complete with black shale horizons that record the OAE1b carbon cycle perturbations, has provided a unique opportunity to address the shortcomings referred to above. High-resolution geochemical proxies (CaCO3, TOC, and delta C-13), along with planktonic foraminifera and calcareous nannofossils, were used to establish an integrated and robust global stratigraphic framework in order to: (1) precisely correlate the prominent black shale horizons of OAE1b in different marine environments (the Vocontian Basin in southeast France, Deep Sea Drilling Project Site 545 and Ocean Drilling Program Hole 1049C in the eastern and western North Atlantic, respectively); and (2) provide an effective tool to reconstruct, in high resolution, the paleobiological, paleoceanographic and paleoclimatic changes across the upper Aptian to lower Albian interval.

The upper Aptian to lower Albian interval (similar to 114-109 Ma) represents a crucial period during Earth's history, with a major evolution in the nature of mid-Cretaceous tectonics, sea level, climate, and marine plankton communities. Interestingly, it also includes multiple prominent black shale horizons that are the sedimentary expression of oceanic anoxic event (OAE) 1b. However, due to a set of geological, stratigraphic, and taxonomic challenges, difficulties constraining this OAE may sometimes result in inaccurate correlation.